Shopify draft order checkout for a custom calculated price

Width 184 cm. Height 92. The calculator says $428. The cart still shows $428. Checkout charges the $89 variant. The millimetres sat in line item properties. Shopify’s checkout does not treat those as the unit price.

Shopify draft order checkout custom price is the other path: intercept the checkout button, create a draft order, send the shopper to that draft’s invoice URL. The app server writes the calculated amount. The theme does not.

Shopify Help Adding variants is still three options and 2048 variants. Not 100. You do not invent 1840 SKUs so the till “happens” to match the PDP. Image mapping for a finish is a different Premium feature — see swap the product image by option. This article is checkout.

Options Price Calculator puts Draft order checkout / Order from admin on the $39.99 plan. Not Free. Not $9.99. Not Premium at $19.99.

The formula dies at /checkout

Checkout totals use variant price, discounts, shipping, tax. The calculator stores `__ooCustomPrice` on the line. Without an intercept, that value is a property. `/checkout` is allowed to ignore it.

`properties[Width]` is a note for fulfillment. It is not a commerce engine. A cart-drawer button that points at native checkout will drop a made-to-measure total the moment the shopper clicks.

Keep real stock as variants (linen vs cotton on a roll). Do not keep millimetres as variants.

Improvised checkouts that leak money

Variant grids for every size. You still cannot offer 92 cm. You type a draft by hand after the “request a quote” form.

Charge $89, fix the order later. Chargebacks. Wrong tax. The warehouse picks against the cheap line.

Admin drafts as a service desk. Shopify drafts are fine. You are the bottleneck.

None of that is: calculator line in the cart → server draft → invoice URL, with the same selections attached.

The $39.99 toggle

Options Price Calculator is Built for Shopify (5.0 from 27 reviews). Unlimited options and formulas without extra variants. Live listing, USD:

• Free — 20 uses; always free on Shopify Develop

• $9.99/month — unlimited options, AI, formula builder, metafields, styling, multilingual

• $19.99/month (Premium) — conditional logic, Font Picker, live preview, price breakdown, lookup tables, file uploads

• $39.99/month — conditional fields, draft-order checkout, admin calculator tools, setup service

Draft order checkout: Settings → Checkout → Create draft order on checkout → Save. New shops leave it off until you save.

Then:

• Theme checkout buttons (cart, mini-cart, drawer) are intercepted where the calculator script runs.

• Cart contents plus line item properties (selections, custom price, signatures, custom image) go to the app server.

• The server creates the draft and returns the invoice URL.

• The shopper pays there.

No calculator lines in the cart → native Shopify checkout. A plain T-shirt does not get drafted.

Embed or it never fires

The storefront script has to load. Enable the Product Calculator app embed on the whole theme, or at least every template that shows a checkout button (cart, product with a quick-add drawer). No embed, no intercept, variant price wins.

Odd button markup: Advanced settings → Custom checkout button selector, e.g. `#CartDrawer-Checkout`. Custom selectors first, built-in list second.

Email is optional. Logged-in or already captured: the draft attaches to that customer. Otherwise a guest draft.

Safety switch

The flow honours server-side price validation. On: each calculator line is verified before the draft exists. Off: `__ooCustomPrice` is trusted as-is. Default for new shops is off until Theme settings are saved. Turn it on for custom prices.

Docs tip: app toggle on, theme settings never saved → shoppers still hit native checkout.

Walkthrough: 184 × 92, fabric as a real SKU

Fabric stays a Shopify option (inventory). Width and height are calculator fields. A formula like `product_price + (width * height)` lives in the Formula Builder. Oversize branching is Premium. The checkout intercept is $39.99.

1. Install or upgrade Options Price Calculator to $39.99.

2. Link products and variants. Theme app block on the product template.

3. Embed on cart and product (drawer).

4. Create draft order on checkout. Save in the app and in theme settings.

5. Enable server-side validation. Save.

6. Test 184 × 92 from the drawer. Admin should show a draft at the calculated total. Guest cart → guest draft. Cart with no calculator line → `/checkout`.

Custom selector if the theme’s button is invisible to the defaults. Live preview and option images do not replace this setting.

Admin draft-order calculator tools are listed on the same $39.99 plan (“Order from admin”). This article is the storefront intercept, not a second builder walkthrough. Conditional fields (show/hide) are also $39.99; they do not create the invoice URL by themselves.

Ajax cart / cart drawer / slide-out cart are on the listing “Works with.” If checkout lives only in a drawer the embed still has to load on that product or cart template — otherwise the drawer’s button is native.

Setup checklist

1. Listing — $39.99 for draft-order checkout. $19.99 is preview and conditionals, not this.

2. Block + embed. Add the extension to the product page.

3. Save the checkout toggle twice (app + theme).

4. Turn validation on.

5. Hit drawer, cart page, quick-add, guest, logged-in. Confirm the draft carries the fields.

Selector picker exists because themes differ. Shopify still caps you at three options and 2048 variants.

Close

Shopify draft order checkout custom price is a $39.99 setting, not a fourth Shopify option. Button → draft → invoice. Empty of calculator lines, checkout stays native. Embed is mandatory. Validate prices on the server.

Turn it on in Options Price Calculator. The shopper types 184 × 92. The invoice already has $428. You do not retype the draft.